Body-weight supported treadmill training (BWSTT) is one therapeutic modality for locomotor training that is rapidly being adopted into physical rehabilitation to improve walking after stroke. While there is preliminary support for the efficacy of this therapeutic modality, the optimal intensity, frequency, and duration for this intervention is not known. There is lack of evidence concerning when delivery of this intervention is most effective post-stroke (e.g. sub-acute: < 1-3 months post-stroke or chronic: > 6 months post-stroke). The primary aim of this clinical trial planning grant is to organize an effective research team and develop the elements essential for conducting a successful randomized clinical trial (RCT) of BWSTT in individuals post-stroke. The proposed clinical trial of BWSTT will be designed to assess: (1) the optimal treatment duration (12 vs. 24 training sessions), (2) the timing of treatment delivery (1 - 3 months post-stroke vs. > 6 months post-stroke), and (3) the effects of severity of locomotor impairments. There are many essential components for the successful implementation of this RCT. Specifically, this planning grant will (1) identify additional collaborators, (2) develop (a) the experimental design and (b) the intervention protocols, (3) select and establish protocols for assessing the primary and secondary outcome measures, (4a) determine the effect size and power needed for clinically meaningful results and (4b) establish an analysis plan, (5) develop a data coordination/management team, (6) assess the feasibility of subject recruitment strategies, (7) select exclusion and inclusion criteria, (8) develop methods to characterize competing interventions, (9) develop a training program to assure that the intervention is replicable across sites, (10) select sites for the RCT and attain Institutional Review Board approval, and (11) develop administrative operations to manage the RCT. The clinical trial planning grant will result in an organized and well-prepared research team ready to conduct an effective RCT of duration and timing of BWSTT and the effect of severity of locomotor impairment on outcomes. The long-term objective is to improve the ability to walk in individuals following stroke by providing clinical practice guidelines, based on scientific evidence, for the optimal use of BWSTT in rehabilitation.